Semiconductor device having contact plug and buried conductive film therein

Abstract

A semiconductor device includes an active element structure that is formed on a semiconductor substrate and has a connection region formed in the surface of the semiconductor substrate. A contact hole extends from a surface of a first insulating film formed on the semiconductor substrate to the connection region. A contact plug is provided in the contact hole. A clearance formed in the contact plug is formed with a buried conductive film consisting of a material different from the contact plug. The buried conductive film has a continuous surface without forming a step with the surface of the contact plug.

1. A semiconductor device comprising:
 a semiconductor substrate; 
 an active element structure formed on the semiconductor substrate, and having a connection region formed in the surface of the semiconductor substrate; 
 a first insulating film provided on the semiconductor substrate; 
 a contact hole extending from a surface of the first insulating film to the connection region; 
 a contact plug provided in the contact hole; 
 a buried conductive film filled in a clearance formed in the contact plug, consisting of a material different from the contact plug, having a continuous surface without forming a step with the surface of the contact plug, and having a first width in the surface of the buried conductive film and a second width larger than the first width in a deeper position than the surface of the buried conductive film; and 
 a first intervention conductive film interposed between an inner surface of the contact hole and the contact plug, the first intervention conductive film and the buried conductive film consisting substantially of the same material. 
 
   
   
     2. The device according to  claim 1 , further comprising:
 a barrier metal provided in an interconnect trench formed on the contact plug and the buried conductive film, and having a bottom surface common to the upper surface of the contact plug and the buried conductive film; and 
 an interconnect layer provided in the interconnect trench, and consisting of a conductive material. 
 
   
   
     3. The device according to  claim 1 , wherein the buried conductive film and the first intervention conductive film consist substantially of a material selected from the group consisting of TiN and TiSiN. 
   
   
     4. The device according to  claim 2 , wherein a film thickness of the first intervention conductive film is equal to or less than 10% of the width of cross section of the interconnect trench. 
   
   
     5. The device according to  claim 1 , wherein the active element structure includes a transistor. 
   
   
     6. The device according to  claim 1 , wherein the contact plug consists substantially of W.